Goniometers are instruments which measure the extent of movement of flexing joints such as the knee, ankle, wrist, shoulders, hips, fingers, etc. After injuries or illnesses which incapacitate a joint, recovery generally requires some form of physical therapy. Success in physical therapy treatment is measured by the extent to which the joint becomes more flexible over time. A modified protractor called a goniometer is placed against the joint and an angular reading of the extent of joint movement is taken as an indication of a patient's response to treatment. Readings are taken over preset intervals of time to plot the patient's progress. In U.S. Pat. No. 1,590,499, a very basic goniometer consisting of a protractor with a moving indicator is described which is strapped onto the limbs surrounding a joint. It has no recording capability and it permits only a direct one-time reading. In U.S. Pat. No. 4,306,571, a goniometer with three potentiometers is attached to a knee for recordation and dynamic joint motion analysis. The device however requires overly cumbersome a-nd expensive separate processing and recording instruments to analyze signals and to graphically record them. The connection to the processing and recording instruments also prevents utilization of the goniometer under real-life movement conditions.
Generally available present day commercial goniometers are usually simple instruments having two legs hinged together with an angular scale. A reading is taken and recorded and the instrument is stored. An example of such simple instrument is described in U.S. Pat. No. 4,771,548. This goniometer has a platform with a planar surface for a foot and a standard protractor-like scale for measurement of ankle flexibility. Newer, significantly more expensive goniometers electronically store joint motion readings of patients for downloading into computers. These goniometers are not however designed for active continuous motion and real life movement measurements but rather for single maximum readings.